Purpose

Allow users to save and manage their own PC builds across sessions, with authentication and ownership enforced by the GraphQL API.

Changes

• Add Firebase Google and email/password login, registration, and logout.
• Link Firebase accounts to users in PostgreSQL.
• Add My builds with private/published labels and keyboard-accessible cards.
• Support reopening, updating, publishing, copying, and deleting owned builds.
• Restrict Community to published builds and preserve ownerless legacy builds.
• Document the authentication provider comparison and database setup.
• Integrate with dev’s routing, component structure, request limits, and query batching.

Related issues

Closes #97

Verification

• Frontend: npm run lint, npm run build, and npm test passed, 97 tests.
• Backend: npm run lint and npm test passed, 95 tests, including the TypeScript build.
• Authorization tests cover two user identities, private access, owner-only updates/deletion, and legacy builds using isolated database fixtures.
• Login and backend user creation were manually tested locally.
• Final deployed VM smoke testing remains outstanding.

Screenshots

Checklist

• I have reviewed my own changes.
• The changes meet the linked issue's acceptance criteria, where applicable.
• I have verified the changes and recorded the results above.
• I have added or updated tests where needed.
• I have updated documentation where needed.
• I have included screenshots for visual changes, or marked them not applicable.